In recent years, electronic devices are highly required to be increased in integration in the electronic device production field represented by integrated circuit device production, and this allows a photolithographic technique for forming fine patterns to be required.
In general, a wavelength of an exposure light source is shortened as means for obtaining fine patterns. To be specific, a UV ray represented by a g beam and an i beam has so far been used therefor, but at present, semiconductor devices in which a KrF excimer laser and an ArF excimer laser are used are initiated to be produced in an industrial scale. Further, a F2 excimer laser, an electron beam, EUV (an extreme UV ray) and an X ray which have shorter wavelengths than those of the above excimer lasers are investigated.
Lithographic characteristics such as a sensitivity to the above light sources and a resolution in which patterns having a fine dimension can be reproduced are required to resist materials.
Chemically amplified photoresist compositions comprising polymers having an acid-dissociable functional group and compounds (herein referred to as “a photoacid generator”) generating acid by irradiation (herein referred to as “exposure”) of a radial ray are used as resist materials satisfying the above requirement.
The above polymer having an acid-dissociable functional group comprises a basic structure in which a part of an alkali-readily soluble site of an alkali-soluble polymer is protected by a suitable acid-dissociable functional group, and selection of the above acid-dissociable functional group is very important in terms of controlling the performances of the photoresist composition.
Known as the existing acid-dissociable functional group are groups having an adamantane structure (refer to a patent document 1 and a non-patent document 1), groups comprising a tetrahydropyranyl group (refer to a patent document 2) and groups comprising a lactone ring (refer to a patent document 3).    Patent document 1: Japanese Patent Application Laid-Open No. 73173/1997    Patent document 2: Japanese Patent Application Laid-Open No. 88367/1993    Patent document 3: Japanese Patent Application Laid-Open No. 46206/2004    Non-patent document 1: Journal of Photopolymer Science and Technology, Vol. 9, No. 3, p. 475 to 487 (1996)